DE 10 2008 043 044 A1 relates to an apparatus for fixing magnets. For the purpose of increasing power by additional permanent magnetic field strength and for the purpose of reducing the magnetic stray flux, permanent magnets are inserted into intermediate spaces between the alternating poles on an electrical machine, said electrical machine being, in particular, a generator for a motor vehicle having an exciter system comprising a large number of electrically excited individual poles in the stator or rotor in the form of electromagnetically excited poles which are axially oriented over the circumferences and of which the polarity alternates with the circumferential direction. Said permanent magnets are held by means of a holding element which cannot be magnetically excited and which is held in pole slots on both sides.
DE 10 2006 041 981 A1 relates to an electrical machine. This electrical machine is, in particular, an electrically excited claw-pole generator for use in a motor vehicle. The claw-pole generator comprises a rotor with a large number of axially oriented poles, of which the magnetization changes in the circumferential direction, and with permanent magnets, which are arranged between the poles, for increasing power and for reducing the stray flux. The permanent magnets are secured by means of metal sheets which cannot be magnetized and are held in pole slots on both sides. These metal sheets each have at least one additional arresting means with which they are supported in the axial and radial direction at the pole flanks with or without stops or guide channels. The additional arresting means are designed, for example, as sheet-metal tabs which are bent or angled and are supported in a sprung manner against at least one axial end section of the poles.
DE 199 51 155 A1 likewise relates to an electrical machine. This electrical machine is a generator for a motor vehicle having an exciter system and a large number of electrically excited individual poles in the stator or in the rotor. In this case, the stator and the rotor are in the form of electromagnetically excited poles which are axially oriented over the circumference and polarity which alternates with the circumferential direction. In order to reduce the magnetic stray flux, permanent magnets are located in the intermediate spaces between the poles. The permanent magnets are inserted into said intermediate spaces. The permanent magnets are attached to the stator and/or to the rotor in such a way that the permanent magnets are each held by means of a holding element which cannot be magnetically excited, with said holding element being held in pole slots by caulking tangentially and axially on both sides and one pole slot being made on the longitudinal side of one pole and one pole slot being made on the longitudinal side of a mating pole which is situated opposite said first pole. The holding element covers the respective permanent magnets with a base region in the radial direction with respect to the stator in the case of a rotor, and in the radial direction with respect to the rotor in the case of a stator. The holding element has bent-away lugs on both opposite ends of the base region, said lugs exerting a clamping force on axial end sides of the permanent magnets used.
In the case of electrical machines such as the electrical machines known from DE 10 2006 041 981 A1 and DE 199 51 155 A1, high rotation speeds, ≧22,000 rpm, result in the claw pole of a claw-pole machine bending open radially outward. This deformation occurs to a greater or lesser extent in each case depending on the rotation speed of the electrical machine,
DE 10 2008 044 187 A1 relates to an electrical machine, in particular a claw-pole generator. The claw-pole generator comprises a large number of poles which are associated with a rotor and have magnetic fields which are oriented in an alternating manner in the circumferential direction. Permanent magnets are arranged between the poles, with the permanent magnets each being attached by way of a clamping clip which has spring elements which are arranged in slots in the adjacent poles, these slots being produced, in particular, without the removal of material, or by way of a spring-ring section or spring ring which is arranged in slots in the permanent magnet and in slots in the adjacent poles, these slots being produced, in particular, without material being removed.
For a high power requirement, permanent magnets can be inserted between the respective claw-pole fingers in the case of claw-pole generators, as described above. Up until this point, the permanent magnets were either directly inserted into spaces which are produced by cutting-machining or adhesively bonded by means of adhesive or using an impregnating agent or fixed and positioned with additional sheet-metal or plastic supports with different specific characteristics. The high positioning and fixing tolerances between the individual components cause mechanical and electromagnetic unbalances and therefore a relatively high load in terms of noise and power losses, and a shorter service life can be expected. To date, these disadvantages, that is to say a relatively high development of noise, power losses and a relatively low expected service life, have had to be accepted in most cases.